Dual leaf suspension for vehicles

ABSTRACT

A vehicle drive arrangement for a vehicle of the type having differential power transmission arrangement that converts the rotatory motion of the rotatory power shaft to rotatory motion of first and second drive shafts disposed substantially orthogonal the rotatory power shaft. Primary leaf springs are each coupled at their respective centers to respective drive shafts by pivotal arrangements. The first and second primary springs may include helical springs that are used in place of, or in combination with, the primary leaf springs. Secondary leaf springs may be splayed and therefore need not be arranged parallel to the primary leaf springs. Control over vehicle kinematics is enhanced by configuring the resilience of a fulcrum bumper using resilient, rheological, or active systems. An active system will control vehicle height while stationary to facilitate loading and unloading of the vehicle.

CROSS-REFERENCES TO RELATED APPLICATIONS

This patent application claims priority to U.S. patent application Ser.No. 12/308,481, filed Sep. 13, 2010, which claims the benefit ofInternational Application Ser. No. PCT/US2007/014290 filed on Jun. 18,2007, which claims the benefit U.S. Provisional Patent Application Ser.No. 60/814,518, filed on Jun. 16, 2006; U.S. Provisional PatentApplication Ser. No. 60/900,796 filed on Feb. 7, 2007; U.S. ProvisionalPatent Application Ser. No. 60/921,881 filed on Apr. 3, 2007, each ofwhich are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

This invention relates generally to suspension systems for vehicles, andmore particularly, to a leaf suspension arrangement that is useable withindependent and semi-independent suspension systems.

DESCRIPTION OF THE RELATED ART

Leaf spring systems have for many years been used for the suspension ofwheeled vehicles. The central element of a leaf spring suspension systemfor a vehicle is termed a “semi-elliptical” spring configured as anarc-shaped length of spring steel having a rectangular cross-section. Atthe center of the arc is provided an arrangement for coupling to theaxle of the vehicle. At the ends are provided coupler holes forattaching the spring to the vehicle body. For heavy vehicles, leafsprings are stacked on one another to form layers of springs ofdifferent lengths. Leaf springs are still used in heavy commercialvehicles and railway carriages. In the case of very heavy vehicles, leafsprings provide the advantage of spreading the load over a larger regionof the vehicle's chassis. A coil spring, on the other hand, willtransfer the load to a single point.

The well-known Hotchkiss drive, the name of which derives from theFrench automobile firm of Hotchkiss, employs a solid axle that iscoupled at its ends to the centers of respective semi-elliptical leafsprings. There are a number of problems with this form of drivearrangement. First, this drive system is characterized by high unsprungmass. Additionally, the use of a solid axle results in coupledleft/right wheel motion. During heavy cornering and fast acceleration,this known system suffers from vertical deflection and wind-up.

One prior art effort to address the problems associated with theHotchkiss system employs a parallel leaf spring arrangement at each endof a solid axle. This known arrangement affords increased axle control,in the form of reduced power hop. Other advantages of this knownarrangement include roll under steer, auto load leveling and the grossvehicle weight, and no frame changes are required to convert from aHotchkiss system. However, the known parallel leaf spring arrangementemploys a solid axle, and therefore does not provide the benefits ofindependent suspension. In addition, this known arrangement is plaguedwith the disadvantage of high unsprung mass.

A de Dion tube vehicle suspension arrangement is a form ofsemi-independent suspension and constitutes an improvement over theHotchkiss drive. In this type of suspension, universal joints areemployed at the wheel hubs and the differential, and there isadditionally provided a solid tubular beam that maintains the opposingwheels in parallel. The de Dion tube is not directly connected to thechassis and is not intended to flex.

The benefits of a de Dion suspension include a reduction in the unsprungweight compared to the Hotchkiss drive. This is achieved by coupling thedifferential to the chassis. In addition, there are no camber changesduring suspension unloading. Since the camber of both wheels is set atzero degrees, the traction from wide tires is improved, and wheel hopunder high power operations is reduced compared to an independentsuspension. However, the de Dion tube adds unsprung weight.

It is, therefore, an object of this invention to provide a vehiclesuspension arrangement that provides the benefits of independentsuspension while using leaf spring technology.

It is another object of this invention to provide a vehicle suspensionarrangement that employs leaf spring technology and yet affords reducedunsprung mass for reduced inertial effects and improved vehicle handlingresponse.

It is also an object of this invention to provide a vehicle suspensionarrangement that employs leaf spring technology and affords reducedsuspension inertia.

It is a further object of this invention to provide a vehicle suspensionarrangement that employs leaf spring technology and affords reducednoise, vibration, and harshness (NVH).

It is additionally an object of this invention to provide a vehiclesuspension arrangement that employs leaf spring technology and affordsreduced lateral wheel shake.

It is yet a further object of this invention to provide a vehiclesuspension arrangement that employs leaf spring technology and affordsreduced side view wind-up at the axle bracket.

It is also another object of this invention to provide a vehiclesuspension arrangement that employs leaf spring technology and affordsreduced forward and rearward movement.

It is yet an additional object of this invention to provide a vehiclesuspension arrangement that employs leaf spring technology and affords asemi-independent suspension effect during asymmetric wheel travel.

It is yet an additional object of this invention to provide a vehiclesuspension arrangement that employs leaf spring technology incombination with a coil spring element.

SUMMARY OF THE INVENTION

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

The foregoing and other objects are achieved by this invention whichprovides a vehicle drive arrangement for a vehicle of the type having achassis extending longitudinally, and a rotary power shaft extendinglongitudinally along the chassis. The rotary power shaft is coupled at arearward end thereof to a differential power transmission arrangementthat converts the rotary motion of the rotatory power shaft to rotatorymotion of first and second drive shafts disposed substantiallyorthogonal the rotary power shaft. Each of the first and second driveshafts has a respective longitudinal axis. In accordance with theinvention, there are provided a differential coupling arrangement forfixedly coupling the differential arrangement to the chassis, and firstand second universal coupling arrangements for coupling respective onesof the first and second drive shafts to the differential arrangement,whereby the first and second drive shafts are transaxially displaceable.First and second spring elements are coupled to respective ones of thefirst and second drive shafts at respective ends distal from the firstand second universal coupling arrangements, and to the chassis. Inaddition, first and second secondary leaf springs are coupled atrespective first ends thereof to the first and second drive shafts atrespective ends distal from the first and second universal couplingarrangements, and at respective second ends thereof to the chassis.There is additionally provided a beam having first and second ends. Thebeam is coupled at the first and second ends to respective ones of thefirst and second drive shafts at respective ends distal from the firstand second universal coupling arrangements.

In one embodiment of the invention, each of the first and second ends ofthe beam are coupled to the first and second drive shafts at adetermined transaxial distance.

In a highly advantageous embodiment, the first and second springelements are respective first and second primary leaf springs. Each ofthe first and second primary leaf springs is coupled at a respectivefirst end thereof to the chassis and at substantially the center thereofto a respective one of the first and second drive shafts. The first andsecond secondary leaf springs are arranged, in this embodiment, to besubstantially parallel to the respective first and second primary leafsprings.

A beam coupler arrangement is provided for coupling the beam to thechassis. The beam coupler arrangement includes a pivotable beam couplerelement pivotally coupled to the beam. A first beam coupler arm iscoupled at one end thereof to the pivotable beam coupler element, and ata distal end thereof substantially in the direction of the longitudinalaxis of the first drive shaft, to the chassis. There is additionallyprovided a second beam coupler arm coupled at one end thereof to thepivotable beam coupler element, and at a distal end thereofsubstantially in the direction of the longitudinal axis of the seconddrive shaft, to the chassis.

In a practicable embodiment of the invention, the first and secondsecondary leaf springs are disposed below the respective first andsecond primary leaf springs. In other embodiments, however, the firstand second secondary leaf springs are disposed above the respectivefirst and second primary leaf springs. In some of such otherembodiments, the first and second secondary leaf springs are arranged toextend through the chassis.

In a highly advantageous embodiment of the invention, there are furtherprovided first and second displaceable pivot coupling arrangements forcoupling the respective second ends of the first and second secondaryleaf springs to the chassis. The displaceable pivot couplingarrangements facilitate adjustment of the effective spring rate of thesecondary leaf springs.

In other embodiments, there are provided first and second displaceablefulcrum arrangements, also for facilitating the varying of therespective spring rates of the first and second secondary leaf springs.

In accordance with a further aspect of the invention, there is provideda vehicle drive arrangement for a vehicle of the type having a chassisextending longitudinally, and a rotatory power shaft extendinglongitudinally along the chassis. The rotary power shaft is coupled at arearward end thereof to a differential power transmission arrangementthat converts the rotary motion of the rotatory power shaft to rotarymotion of first and second drive shafts disposed substantiallyorthogonal the rotary power shaft. Each of the first and second driveshafts has a respective longitudinal axis. In accordance with theinvention, there are provided a differential coupling arrangement forfixedly coupling the differential arrangement to the chassis, and firstand second universal coupling arrangements for coupling respective onesof the first and second drive shafts to the differential arrangement,whereby the first and second drive shafts are transaxially displaceable.First and second primary leaf springs are each coupled at respectivefirst and second ends thereof to the chassis and at substantially thecenter thereof to respective ones of the first and second drive shaftsat respective ends of the drive shafts distal from the first and seconduniversal coupling arrangements. In addition, first and second secondaryleaf springs are coupled at respective first ends thereof to the firstand second drive shafts at respective ends distal from the first andsecond universal coupling arrangements, and at respective second endsthereof to the chassis. There is additionally provided a beam havingfirst and second ends. The beam is coupled at the first and second endsto respective ones of the first and second drive shafts at respectiveends distal from the first and second universal coupling arrangements.

In a highly advantageous embodiment of the invention, there is provideda vehicle suspension arrangement for a vehicle having a chassis and adrive axle. The vehicle suspension arrangement is provided with aprimary leaf spring having a substantially longitudinal configurationand first and second ends for coupling to the chassis of the vehicle. Asecondary leaf spring has a substantially longitudinal configuration, afirst end for coupling to the chassis, and a second end. A couplingelement is provided for coupling to the drive axle. In addition, a firstpivot joint for pivotally coupling to substantially the center of saidprimary leaf spring intermediate of its first and second ends forcoupling to said coupling element. Finally, a second pivot joint forpivotally coupling the second end of said secondary leaf spring to saidcoupling element.

In one embodiment, there is further provided a primary leaf coupler forsecuring said first pivot joint to substantially the center of saidprimary leaf spring. The first pivot joint is formed of first and secondpivot portions, the first pivot portion being fixedly coupled to saidprimary leaf coupler, and the second pivot portion being fixedly coupledto the coupling element. The first and second pivot portion beingconfigured to be pivotally coupled to each other.

In a still further embodiment, the first pivot joint is configured toenable limited pivotal motion between said primary leaf spring and saidcoupling element. The pivotal motion in this embodiment therefore isdirected longitudinally in see-saw like relation to said primary leafspring.

In accordance with a further apparatus aspect of the invention, there isprovided a vehicle suspension arrangement for a vehicle having a chassisand a drive axle. The vehicle suspension arrangement is provided with aprimary spring having a substantially helical configuration, the primaryspring having a first end for coupling to the chassis of the vehicle,and a second end for coupling to an axle of the vehicle. A secondaryleaf spring that has a substantially longitudinal configuration isfurther provided. The secondary leaf spring has a first end for couplingto the chassis, and a second end. Additionally, a coupling elementcouples the second ends of the secondary leaf spring to the drive axle.

In one embodiment of the vehicle suspension arrangement, the couplingelement includes a pivot joint for pivotally coupling the second end ofsaid secondary leaf spring to the drive axle.

In a still further embodiment of the invention, there is provided afurther primary spring having respective first and second ends thereofcoupled to the chassis. The further primary spring is coupled atsubstantially the center thereof to the drive shaft and to the second enof said primary spring. In a highly advantageous embodiment, the furtherprimary spring is a flat locating plate. The flat locating plate is, insome embodiments, a single plate-main leaf spring.

BRIEF DESCRIPTION OF THE DRAWINGS

Comprehension of the invention is facilitated by reading the followingdetailed description, in conjunction with the annexed drawing, in which:

FIG. 1 is a perspective representation of a specific illustrativeembodiment of the invention;

FIG. 2 is a side plan view of the embodiment of FIG. 1;

FIG. 3 is a perspective representation of a further specificillustrative embodiment of the invention;

FIGS. 4 a and 4 b are respective side plan and partially cross-sectionalfront plan simplified schematic illustrations of a rotary jointarrangement constructed in accordance with the principles of theinvention;

FIGS. 5 a and 5 b are simplified representations of a suspension systemconstructed in accordance with the principles of the invention (FIG. 5a) and a prior art suspension arrangement (FIG. 5 b), both in asimulated static acceleration condition;

FIGS. 6 a and 6 b are simplified representations of the suspensionsystem constructed in accordance with the principles of the invention ofFIG. 5 a and a prior art suspension arrangement of FIG. 5 b, both in asimulated static braking condition;

FIG. 7 is a simplified schematic representation of a side view of asuspension system constructed in accordance with the principles of theinvention with a 1^(st) stage leaf spring, and further showing the wheelcenter path, with a fulcrum arranged to communicate with the 2 ^(nd)stage lower leaf;

FIG. 8 is a simplified schematic representation of a side view of asuspension system constructed in accordance with the principles of theinvention with a 1^(st) stage consisting of a substantially equivalentcoil spring, or air spring, with the fulcrum of the 2^(nd) stage lowerleaf removed;

FIG. 9 is a simplified schematic representation of a side view of asuspension system constructed in accordance with the principles of theinvention with a 1^(st) stage consisting of a coil spring or air spring,with an optional fulcrum, arranged to communicate with the secondarystage lower leaf, and further showing an optional locating spring platein the 1^(st) stage;

FIG. 10 is a simplified schematic representation of a clip bracket thatcan be used to push or pull the main spring or the secondary stage;

FIGS. 11 a, 11 b, and 11 c are simplified schematic side viewrepresentations of a height control arrangement constructed inaccordance with the invention that is useful in the loading andunloading of a stationary vehicle, FIG. 11 a showing a simplified systemcontrol arrangement in block and line form;

FIG. 12 is a simplified schematic top plan representation of a splayedsuspension arrangement constructed in accordance with the inventionwherein secondary leaf springs are shown to be mounted at angles withrespect to the primary leaf springs;

FIG. 13 is a simplified schematic perspective representation of avariable position fulcrum bumper constructed in accordance with theinvention that may be active or passive to rotate in a controlled mannerto create a variation in the stiffness of the secondary spring rate;

FIG. 14 is a simplified schematic plan representation of the variableposition fulcrum bumper of FIG. 13; and

FIG. 15 is a simplified schematic representation of the variableposition fulcrum bumper of FIG. 14 that is useful to illustrate thevariation in vehicle height that is achievable, particularly when thevehicle (not shown) is stationary.

DETAILED DESCRIPTION

FIG. 1 is a perspective representation of a specific illustrativeembodiment of the invention. As shown in this figure, a vehiclesuspension system 100 has a chassis that is generally designated aschassis 110. The chassis has a pair of substantially parallel chassisrails 112 a and 112 b that are coupled to one another by cross-braces116 and 118.

A differential drive arrangement 120 is fixedly coupled to the chassisand converts the rotary motion of a drive shaft 122 to substantiallyorthogonal rotary motion at half shafts 125 a and 125 b. Each half shafthas an associated pair of universal joints (not specifically designated)that are arranged to be proximal and distal with respect to thedifferential drive arrangement Thus, the half shafts, each of which hasan associated longitudinal axis (not shown), accommodate transaxialmotion, particularly by operation of the proximal universal joints.

Half shafts 125 a and 125 b are shown to be coupled at their distal endsto respective leaf springs 130 a and 130 b. Referring to leaf spring 130a, for example, the leaf spring is, in this specific illustrativeembodiment of the invention, pivotally coupled at its forward end to abracket 132 a. At its rearward end, leaf spring 130 a is pivotallycoupled to a link 134 a. As shown in this figure, there is additionallyprovided a half leaf spring 136 a that is also, in this specificillustrative embodiment of the invention, coupled at its forward end tobracket 132 a. At its rearward end, half leaf spring 136 a is coupled tothe distal end of half shaft 125 a. Half leaf spring 136 a is shown inthis specific illustrative embodiment of the invention, to engage afulcrum 133 a.

There is additionally provided a transverse beam 140 that is coupled tocross-brace 116 by a damper 142 and to cross-brace 118 by a furtherdamper 144. Transverse beam 140 has installed thereon a pivoting member150 to which are attached link elements 152 and 154. The link elementsare attached, via brackets (not specifically designated), to cross-brace118.

FIG. 2 is a side plan view of the embodiment of FIG. 1 of vehiclesuspension system 100. Elements of structure that have previously beendiscussed are similarly designated. As shown in this figure, leaf spring130 a and half leaf spring 136 a are each coupled at their respectiveforward ends to bracket 132 a. Leaf spring 130 a is pivotally coupled ata pivot 160, and half leaf spring 136 a is pivotally coupled at a pivot162, at bracket 132 a. In this specific illustrative embodiment of theinvention, pivots 160 and 162 are fixed on bracket 132 a, which is fixedin relation to chassis rail 112 a. In other embodiments, and as will bedescribed below, there is provided a mechanism (not shown in thisfigure) that displaces bracket 132 a, and in some embodiments, onlypivot 162, in relation to chassis rail 112 a. Such displacement of thepivots enables advantageous adjustment of the combined spring rate ofleaf spring 130 a and half leaf spring 136 a. Additionally, suchdisplacement is useful to adjust the height of the vehicle (not shown)while stopped, illustratively to facilitate loading and unloading ofcargo and passengers (not shown).

FIG. 3 is a perspective representation of a further specificillustrative embodiment of the invention. Elements of structure thathave previously been discussed are similarly designated. As shown inthis figure, a vehicle suspension system 170 has a leaf spring 171 and ahalf leaf spring 172. In contrast to the embodiment of FIGS. 1 and 2,leaf spring 171 is arranged to be coupled to the underside of half shaft125 b. Half leaf spring 172 is coupled above half shaft 125 b.

Leaf spring 171 is, in this specific illustrative embodiment of theinvention, coupled to a bracket 175. Half leaf spring 172 is coupled tochassis rail 177 at a bracket 180. Bracket 180 is shown to be disposedwithin chassis rail 177. It is particularly noteworthy that in thisembodiment half leaf spring 172 is arranged to extend through chassisrail 177 at a fulcrum point 182. The arrangement of this embodimentadvantageously reduces the extent to which the leaf suspension system isvisible when installed on a vehicle.

FIGS. 4 a and 4 b are respective side plan and partially cross-sectionalfront plan simplified schematic illustrations of a rotary jointarrangement 200 constructed in accordance with the principles of theinvention. Elements of structure that bear analogous correspondence toelements of structure that have previously been discussed are similarlydesignated in this figure. Referring to FIG. 4 a, it is seen that thereis provided a leaf spring 130 a that, in this specific illustrativeembodiment of the invention, is pivotally coupled at its forward andrear ends, as previously described. There is additionally provided ahalf leaf spring 210 that is also, in this specific illustrativeembodiment of the invention, pivotally coupled at a pivot mount 212 atits end distal to a further pivotal mounting 213 at a coupling member214. The coupling member is itself coupled to axle shaft 215. Half leafspring 210 is shown in this specific illustrative embodiment of theinvention to engage a fulcrum 216.

FIG. 4 a further illustrates a pivot link mounting arrangement 220wherein leaf spring 130 a is securely clamped between clamping member222 and 224, as will be described below in relation to FIG. 4 b.Referring once again to FIG. 4 a, clamping member 224 is coupled to apivot joint 226 that is itself engaged with coupling 214. Thisarrangement permits a further degree of motion that reduce systeminternal loading on the pivot joint arrangement and leaf springelements.

FIG. 4 b is a partially cross-sectional front plan simplified schematicillustrations of rotary joint arrangement 200 constructed in accordancewith the principles of the invention. Elements of structure that bearanalogous correspondence to elements of structure that have previouslybeen discussed are similarly designated in this figure. It is seen inthis figure that leaf spring 130 a (shown cross-sectionally) is securelyclamped between clamping members 222 and 224 by operation of bolts 230.

Pivot joint 226 is shown in FIG. 4 b to be formed of two pivot sections,214 a and 224 a. More specifically, pivot section 214 a is coupled tocoupling 214 (not specifically designated in this figure), and pivotsection 224 a is coupled to clamping member 224. The pivot sections inthis specific illustrative embodiment of the invention, are pivotallyengaged in this embodiment of the invention in a hinge-like manner.Therefore, in this embodiment, the pivotal motion is directedlongitudinally in see-saw like fashion of leaf spring 130 a.

FIGS. 5 a and 5 b are simplified representations of a suspension system200 constructed in accordance with the principles of the invention (FIG.5 a) and a prior art suspension arrangement 300 (FIG. 5 b),illustratively a conventional parallel leaf suspension, both representedin computer-simulated static acceleration conditions. Elements ofstructure that have previously been discussed are similarly designatedin this figure. FIGS. 5 a and 5 b are situated next to one another forsake of facilitating comparison of the effect of acceleration. It isseen that the prior art embodiment of FIG. 5 b does not comprise thestructural equivalent of half leaf spring 210 shown in FIG. 5 a.

As can be seen in FIG. 5 a, leaf spring 130 a remains essentiallywithout distortion during simulated vehicle acceleration as the vehicle(not shown) travels in the direction shown by arrow 201. Prior artsuspension arrangement 300, on the other hand, shows during thesimulated vehicle acceleration in the direction of arrow 301 adistortion in leaf spring 302 wherein region 313 of leaf spring 302 isdistorted downward and region 314 is distorted upward. This condition,which is commonly referred to as “side view windup,” results in theunacceptable condition of power hop during acceleration, as well as adisadvantageous reduction in axle control.

FIGS. 6 a and 6 b are simplified representations of suspension system200 of FIG. 5 a and prior art suspension arrangement 300 of FIG. 5 b,both in computer-simulated static braking conditions. Elements ofstructure that have previously been discussed are similarly designatedin this figure. As shown in FIG. 6 a, leaf spring 130 a remainssubstantially in its base line configuration during simulatedacceleration in the direction of arrow 201. FIG. 6 b, on the other hand,shows leaf spring 302 to undergo significant side view windup. Region313 of leaf spring 302 is distorted upward significantly, while region314 is distorted downward. When leaf spring 302 is wound up as shown inthis simulation, its spring rate is changed significantly, as well asother suspension parameters, resulting in reduced control, particularlywhen braking is performed on an uneven or bumpy surface (not shown).

FIG. 7 is a simplified schematic representation of a side view of asuspension system 400 constructed in accordance with the principles ofthe invention with a 1^(st) stage leaf spring 410, and further showingthe path of the center of axle 411, as indicated by curved arrow 412with a fulcrum 414 arranged to communicate with 2^(nd) stage lower leafspring 416. The embodiment of the invention represented in this figureis pivotally coupled to 1^(st) stage leaf spring 410 at a pivot coupling414.

FIG. 8 is a simplified schematic representation of a side view of asuspension system 430 constructed in accordance with the principles ofthe invention. Elements of structure that previously have been discussedare similarly designated in this figure. In this figure, there isillustrated a 1^(st) stage consisting of a coil spring 435, which may,in certain embodiments be a conventional air spring (not shown). Instill further embodiments of the invention, coil spring 435 mayconstitute a combination of a coil spring and an air spring. Coil spring435 is substantially equivalent in function to 1^(st) stage leaf spring410 of the embodiment of FIG. 7. However, as will be noted below, theuse of a coil spring results in a variation in the path of the axle.

Fulcrum 414 of the 2^(nd) stage lower leaf has been removed, but isnevertheless illustrated in phantom representation to show that its useis optional in this specific illustrative embodiment of the invention.Its use will depend on the geometric needs of the vehicle (not shown).

In this embodiment, the path of center of axle 411 is indicated bycurved arrow 437. Curved arrow 412, which represents the path of thecenter axle in the embodiment of FIG. 7, is shown in this figure forcomparison purposes.

A significant aspect of this specific illustrative embodiment of theinvention is that lower leaf spring 440 is configured as a lower linksubcomponent that allows a measure of compliance. It is not a rigidlink.

FIG. 9 is a simplified schematic representation of a side view of asuspension system 450 constructed in accordance with the principles ofthe invention with a 1^(st) stage consisting of a substantiallyequivalent coil spring 455, which in some embodiments of the inventionmay be an air spring or a combination of a coil spring and an airspring. Coil spring 455 provides vertical load support in place of1^(st) stage leaf spring 410 shown in FIG. 7. However, in this specificillustrative embodiment of the invention, added control is achieved bythe use of an optional single plate main leaf spring 457 as part of the1^(st) stage with coil spring 455. A lower leaf 460 of the 2^(nd) stageis employed for additional control. In this embodiment, lower leaf 460permits a measure of compliance and is not a rigid link.

Again, Fulcrum 414 of the 2^(nd) stage lower leaf has been removed, butis illustrated in phantom representation to show that its use isoptional in this specific illustrative embodiment of the invention. Itsuse will depend on the geometric needs of the vehicle (not shown).

In this specific illustrative embodiment of the invention, the center ofaxle 411 travels along a path that conforms to curved arrow 462, as seenin the present side view.

FIG. 10 is a simplified schematic representation of a clip bracket 500that can be used to push or pull a stack of spring plates 502. Springplates 502 may be the main spring or the secondary stage in the practiceof the invention. In operation, clip bracket 500 is urged upward anddownward in the direction of arrows 504 and 506, respectively. Springplates 502 are contained between rubber bushings 510 and 512, to preventdamage to the spring plates. The operation of clip bracket 500 will bedescribed below in relation to FIGS. 11 a, 11 b, and 11 c.

FIGS. 11 a, 11 b, and 11 c are simplified schematic side viewrepresentations of a height control arrangement 520 constructed inaccordance with the principles of the invention that is useful in theloading and unloading of a stationary vehicle, FIG. 11 a showing asimplified system control arrangement in block and line form. Elementsof structure that have previously been discussed are similarlydesignated in these figures.

As shown in FIG. 11 a, a primary leaf spring 130 a is coupled at itsends to a chassis rail (not specifically designated) as described inrelation to FIGS. 1 and 2, above. Leaf spring 130 a and secondary spring502, which may be the equivalent of half leaf spring 136 a describedabove, are coupled to the axle (not specifically designated in thisfigure). Moreover, although clip bracket 500 is shown in this specificillustrative embodiment of the invention, to operate on the secondaryspring system, other embodiments can employ clip bracket 500 on theprimary spring, i.e., primary leaf spring 130 a. The principle is toprovide a way literally push or pull on the spring assembly in a localarea to force a temporary camber change This translates into a change inthe height “Z” of the vehicle (see, FIG. 15 and its correspondingdescription below) that can be selectively employed in response to theoperation of a height control system that is generally designated as 530in the figure.

Height control system 532 includes a height control system 532 thatreceives vehicle height information from a height sensor 534. A desiredvehicle height is entered by a user (not shown) at user input 536. In asimple embodiment of the invention, user input 536 may constitute asimple pair of switches (not shown) that enable the user to raise orlower the vehicle height as desired. In other embodiments, user input536 may constitute a programable arrangement (not shown) wherein severalvehicle heights and other conditions can be preprogramed. In response tothe data received at user input 536 and the corresponding height datareceived from height sensor 534, height control system 532 operates anelectrical or hydraulic system (not shown) that exerts a force on clipbracket 500 whereby the clip bracket is urged upward or downward, as thecase may be, in the direction of arrows 504 and 506, respectively,relative to the chassis rail. In this embodiment of the invention, clipbracket 500 can only exert force on secondary spring 502 statically andmust be withdrawn to a baseline condition when the vehicle is in use toprevent damage to the spring. More specifically, the compression surfaceof the spring should not be loaded during dynamic or fatigue loading,and secondary spring 502 should therefore be employed only statically,such as for loading and unloading the vehicle. For this reason, thisspecific illustrative embodiment of the invention is provided with avehicle interface 538 that, among other functions, disables theoperation of height control system 532 when vehicle motion is detected.

If the vehicle is lightly loaded, a height sensor 534 provides vehicleheight data that indicates that clip bracket 500 must pull on secondaryspring 502 such that vehicle trim position is lowered. This allows thevehicle to be loaded more easily by the user. In some embodiments of theinvention, when the vehicle is shifted to the “drive” position, vehicleinterface 538 instructs height control system 532 to restore the heightof the vehicle to a predetermined baseline position to avoid creating arise in the operational stress applied to secondary spring 502.

Referring to FIG. 11 b, it is noted that as the clip bracket (notspecifically designated in this figure) is urged upward in the directionof arrow 504, the vehicle height is reduced from the baseline of Z toZ′, where Z′502 upward, a downward force 542 is applied at the distalend of secondary spring 502.

In FIG. 11 c, the clip bracket (not specifically designated in thisfigure) is urged downward in the direction of arrow 506, the vehicleheight is increased from the baseline of Z to Z″, where Z″>Z. As theclip bracket urges secondary spring 502 upward, an upward force 544 isapplied at the distal end of secondary spring 502.

FIG. 12 is a simplified schematic top plan representation of a splayedsuspension arrangement 560 constructed in accordance with the inventionwherein secondary leaf springs 562 a and 562 b are shown to be mountedat angles with respect to respective ones of primary leaf springs 130 aand 130 b. Elements of structure that have previously been discussed aresimilarly designated in this figure. The secondary leaf springs are notparallel to the respective primary leaf springs, as is the case in theembodiments of FIGS. 1 and 2. In a practical embodiment of theinvention, angles of deviation for the secondary leaf springs will be onthe order of 5°-10°. Of course, the present invention is not limited tothis angular range, which can be determined in response to finiteelement and kinematic analyses as will be discussed below.

Further in relation to the embodiment of FIG. 12, it is noted that theaddition of secondary leaf springs 562 a and 562 b, which are mounted inthe system at an angle relative to primary leaf springs 130 a and 130 b,enhances axle control, as the present non-parallel arrangement emulatesa rigid 4-link rear axle system (not shown).

However, a key difference is that in the present system leaf springs 562a and 562 b function as springs, not just rigid links. This significantdifference allows for compliance that will affect all aspects of thedynamic and kinematic response, including axle wind-up and rollresponse. The angularly disposed secondary springs of this embodiment ofthe invention will increase roll stiffness significantly. The resultingstresses that are applied by this arrangement to the mounting plate (notspecifically designated) can be balanced on a case-by-case basis usingstandard analytical systems, such as finite element analysis (“FEA”).Additionally, kinematic analysis performed using commercially availablesoftware, such as the ADAMS software, will on a case-by-case basisidentify exact values for the vehicle response to roll inputs. Wheelsideslip and axle steer control are thereby improved.

FIG. 13 is a simplified schematic perspective representation of avariable position fulcrum bumper 570 constructed in accordance with theinvention that may be active or passive to rotate in a controlled mannerto create a variation in the stiffness of the secondary spring rate. Byallowing the fulcrum bumper (whether passive or active) to rotate in acontrolled manner about the ground point on the frame bracket, a changein secondary plate stiffness is produced. Essentially, the bumper groundpoint at chassis rail 112 b is rotated such that the point of contact onthe secondary spring is moved. The resulting stiffness and kinematiceffects are significantly affected. The specific value of the amounts ofstiffness and kinematic effects is determined on a case-by-case basiswith the use of kinematic modeling. Additionally, the resulting changein spring rate thereby calculated.

In the practice of this aspect of the invention, an electric motor (notshown) is mounted to the frame bracket (not specifically designated) andis actuated to cause the desired rotation after a signal sent from aheight transducer identifies how much rotation is needed. A simplifiedheight analysis system is described in relation to FIG. 11 a. Thedisplaceable fulcrum bumper herein described can be used in combinationwith a bumper having a variable stiffness, whereby numerous combinationsof final stiffness and kinematic path result. In some embodiments of theinvention, variable position fulcrum bumper 570 comprises a rheologicalmaterial that changes viscosity or stiffness in response to theapplication of electrical energy. The stiffness of variable positionfulcrum bumper 570 is the focus. By activating the fulcrum bumper tobecome more (or less) rigid, a desired change in supporting springstiffness is effected and, correspondingly, the geometric and kinematicattributes of the suspension system are affected.

The fulcrum bumper is not limited to be used in combination with arheological material, and can employ an air spring or other mechanicalmeans to effect the engagement of the secondary stage leaf. Although inthis embodiment of the invention there would be no “active” vehicleretrim, the system could “passively” allow for the rate change, which asa result of the linked kinematic geometry effect, would affect vehicledynamic behavior in roll, acceleration, braking, or cornering motions.Once vehicle attitude is effected via suspension displacement activity,the secondary plate contact with the fulcrum bumper would initiatereaction forces. A variable rate bumper made of rubber, urethane, likematerial that can be voided or otherwise manufactured to cause anonlinear compression effect that will influence the secondary platedeflection character while under load, albeit to a lesser degree than anactive system.

FIG. 14 is a simplified schematic plan representation of the variableposition fulcrum bumper of FIG. 13, that has been magnified tofacilitate the illustration of certain details of its operation. It isseen in this figure that variable position fulcrum bumper 570 isinstalled on a carrier 575 that is configured to pivot about a pivotcoupling 580 to which is also coupled primary leaf spring 130 a. Thecarrier is coupled to half leaf spring 136 a at pivot coupling 582. Anelectric drive arrangement 590 (shown schematically) is actuatable,illustratively in response to the system described in connection withFIG. 11 a, to cause carrier 575 to be rotated about pivot coupling 580in the direction of arrow 596. Electric drive arrangement 590 is coupledto carrier 575 by a drive coupler 592 that, in this specificillustrative embodiment of the invention, is urged in the directions oftwo-headed arrow 593. The actuation of the carrier by electric drivearrangement 590 causes variable position fulcrum bumper 570 to changethe point at which it communicates with half leaf spring 136 a over arange c, whereby half leaf spring 136 a is displaced to position 136 a′,and primary leaf spring 130 a is displaced to position 130 a′.

FIG. 15 is a simplified schematic representation of the variableposition fulcrum bumper of FIG. 14 that is useful to illustrate thevariation in vehicle height that is achievable, particularly when thevehicle (not shown) is stationary. Elements of structure that havepreviously been discussed are similarly designated in this figure. Asshown in this figure, variable position fulcrum bumper 570 causes, aspreviously noted, half leaf spring 136 a is displaced to position 136a′. This displacement is responsive to a displacement of z′ at the pointidentified by line 600. The height displacement of the vehiclecorresponds substantially to the displacement z′ multiplied by themechanical advantage nx/x, or n. In a typical vehicle, the value of nmay be on the order of 6, and therefore the height of the vehicle willbe lowered by approximately 6 z′.

Although the invention has been described in terms of specificembodiments and applications, persons skilled in the art may, in lightof this teaching, generate additional embodiments without exceeding thescope or departing from the spirit of the invention herein claimed.Accordingly, it is to be understood that the drawing and description inthis disclosure are proffered to facilitate comprehension of theinvention, and should not be construed to limit the scope thereof.

Having thus described the invention,

It is claimed:
 1. A vehicle drive arrangement for a vehicle of the typehaving a chassis extending longitudinally, and a rotatory power shaftextending longitudinally along the chassis, the rotatory power shaftbeing coupled at a rearward end thereof to a differential arrangementfor converting the rotatory motion of the rotatory power shaft rotatorymotion of first and second drive shafts have a respective longitudinalaxis, the vehicle drive arrangement comprising: a differential couplingarrangement for fixedly coupling the differential arrangement to thechassis; first and second universal coupling arrangement for couplingrespective ones of the first and second drive shafts to the differentialarrangement, whereby the first and second drive shafts are transaxiallydisplaceable; first and second spring elements coupled to respectiveones of the first and second drive shafts at respective ends distal fromsaid first and second universal coupling arrangements, and to thechassis; first and second secondary leaf springs coupled at respectivefirst ends thereof to the first and second drive shafts at respectiveends distal from said first and second universal coupling arrangements,and at respective second ends thereof to the chassis; and a beam havingfirst and second ends, said beam being coupled at the first and secondends to respective ones of the first and second drive shafts atrespective ends distal from said first and second universal couplingarrangements, said first and second spring elements are respective firstand second primary leaf springs each coupled at respective first endsthereof to the chassis and at substantially the center thereof torespective ones of the first and second drive shafts, said first andsecond secondary leaf springs are disposed above said respective firstand second primary leaf springs.
 2. The vehicle drive arrangement ofclaim 1, wherein said first and second secondary leaf springs arearranged to extend through the chassis.
 3. The vehicle drive arrangementof claim 1, wherein said first and second secondary leaf springs arearranged to be substantially parallel to said respective first andsecond primary leaf springs.
 4. A vehicle suspension arrangement for avehicle having a chassis and a drive axle, the vehicle suspension to thechassis of the vehicle; a secondary leaf spring having a substantiallylongitudinal configuration, a first end for coupling to the chassis, anda second end; a coupling element for coupling to the drive axle; a firstpivot joint for pivotally coupling to substantially the center of saidprimary leaf spring intermediate of its first and second ends forcoupling to said coupling element; and a second pivot joint forpivotally coupling the second end of said secondary leaf spring to saidcoupling element.
 5. The vehicle suspension arrangement of claim 4,wherein there is further provided a primary leaf coupler for securingsaid first pivot joint to substantially the center of said primary leafspring.
 6. The vehicle suspension arrangement of claim 5, wherein saidfirst pivot joint is formed of first and second pivot portions, saidfirst pivot portion being fixedly coupled to said primary leaf coupler,and said second pivot portion being fixedly coupled to said couplingelement, said first and second pivot portion being configured to bepivotally coupled to each other.
 7. The vehicle suspension arrangementof claim 5, wherein said first pivot joint is configured to enablelimited pivotal motion between said primary leaf spring and said coupledelement, the pivotal motion being directed longitudinally in see-sawlike relation to said primary leaf spring.
 8. A vehicle suspensionarrangement for a vehicle having a chassis and a drive axle, the vehiclesuspension arrangement comprising: a primary spring having asubstantially helical configuration, said primary spring having a firstend for coupling to the chassis of the vehicle, and a second end forcoupling to an axle of the vehicle; a secondary leaf spring having asubstantially longitudinal configuration, said secondary leaf springhaving a first end for coupling to the chassis, and a second end; and acoupling element for coupling the second ends of said secondary leafspring to the drive axle.
 9. The vehicle suspension arrangement of claim8, wherein said coupling element comprises a pivot joint for pivotallycoupling the second end of said secondary leaf spring to the drive axle.10. The vehicle suspension arrangement of claim 8, wherein there isprovided a further primary spring having respective first and secondends thereof coupled to the chassis, and being coupled at substantiallythe center thereof to the drive shaft and to the second end of saidprimary spring.
 11. The vehicle suspension arrangement of claim 10,wherein said further primary spring comprises a flat locating plate. 12.The vehicle suspension of claim 11, wherein said further primary springcomprises single plate main leaf spring.
 13. A vehicle suspensionarrangement comprising: a primary leaf spring having a plan viewlongitudinal configuration and first and second ends for coupling to thechassis of the vehicle; a secondary leaf spring having a plan viewlongitudinal configuration, a first end for coupling to the chassis, anda second end; wherein the plan view longitudinal configuration of saidsecondary leaf spring is arranged to be angularly displaced with respectto the plan view longitudinal configuration of said primary leaf spring.14. The vehicle suspension arrangement of claim 13, wherein the planview longitudinal configuration of said secondary leaf spring and theplan view longitudinal configuration of said primary leaf spring areangularly displaced with respect to each other by an angle ofapproximately between 5 to
 10. 15. The vehicle suspension arrangement ofclaim 14, wherein the plan view longitudinal configuration of saidprimary leaf spring is arranged substantially parallel to a chassisframe rail of the vehicle.